The rest of this site exists to answer one question: can I plant it — will this thing survive in your climate and your soil? This page is about the companion question, the one that arrives a moment later. Should you?
It isn't a list of banned plants, and it isn't a lecture. It's a way of thinking about the plants we choose, and the places they tend to end up.
Gardens are made places
No garden is wild. Every garden is a made place — a plantscape assembled from species gathered out of their original homes and arranged to please us. That isn't a flaw; it's simply what a garden is.
Made places sit on a spectrum. At one end, a planting works with the local ecology, leaning on plants that belong and the insects and birds that evolved alongside them. At the other, a garden fights its surroundings, held together only by constant water, feeding and weeding. Most gardens live somewhere in between — and where yours sits is a choice worth making on purpose.
How a garden plant becomes a weed
Very few weeds set out to be weeds. Most begin as ornamentals — chosen, planted and admired — and then they leave. A plant escapes the garden through the same short list of routes: seed carried on the wind or in mud, runners creeping under the fence, birds eating the berries and dropping them a paddock over, a pile of clippings tipped at the edge of a reserve.
Give a hardy plant one of those openings and a few good seasons, and a garden bed quietly becomes a bridgehead.
Garden escapes around the world
The unsettling part is that it's mutual. Almost every country's treasured native is some other country's nightmare. The plants below are loved somewhere and feared somewhere else — select a card to see how each one travelled.
A tragedy of the commons
Here is the hard part. My single plant, in my single garden, is almost never the problem. It's pretty, it's well-behaved, it stays where I put it. The weed problem is the sum of thousands of those gardens — a shared landscape degraded a little by each of us and badly by all of us together.
No single gardener causes it. Collectively, we do. That's exactly what makes it so easy to look away from.
Questions worth asking first
Before a new plant goes in the ground, a few questions are worth a minute of searching:
Native isn't a free pass
Planting natives is usually the safer bet — a local plant rarely runs riot in the place it came from, where its pests and competitors keep it honest. But native is a slippery word. Native to where?
A plant native to one corner of a country can be a serious weed two states away, where the climate suits it but none of the checks from its home exist. Native is regional, not national — the eucalypts above are native somewhere, too.
It's not all or nothing
None of this is an argument against gardens, or against exotic plants. Most garden plants will never go anywhere at all. Exotics aren't villains, and a love of the unusual isn't a crime.
The point isn't guilt — it's attention. Knowing which few plants carry real risk, in your particular place, is most of the work. The rest is just gardening.
Where to check
A few minutes on the right list settles most questions: